The invention described herein generally relates to Software Defined Radios (SDR) and SDR systems. In particular, a system and method of providing bounded dynamic waveform priority allocation for software defined radios is described.
Software Defined Radio methodology is rapidly gaining favor as a way to architect and design radio communication systems with greatly improved interoperability and ability to accommodate future waveform variants. SDR refers to wireless communication in which the transmitter modulation is generated or defined by a computer, and the receiver uses a computer to recover the signal intelligence. To select the desired modulation type, the proper programs are run by microcomputers that control the transmitter and receiver.
A typical voice SDR transmitter, such as may be used in mobile two-way radio or cellular telephone communication, includes the following stages: Microphone; Audio amplifier; Analog-to-digital converter (ADC) that converts the voice audio to digital data; Digital Signal Processor (DSP) to convert the digital data to a form for modulation; Modulator that impresses the digital intelligence onto a radio-frequency (RF) carrier; Series of amplifiers that boosts the RF carrier to the power level necessary for transmission; and Transmitting antenna. Typically, the ADC and Modulator functions are carried out by computer-controlled circuits whose parameters are determined by software, in an SDR. A typical data SDR replaces the microphone, Audio amplifier, and ADC front end components with a computing system providing a data stream to the DSP stage.
A typical receiver designed to intercept the above-described voice SDR signal may employ the following stages, essentially reversing the transmitter's action: Receiving antenna; Superheterodyne system that boosts incoming RF signal strength and converts it to a lower frequency; Demodulator that separates the baseband signal from the RF carrier; Digital signal processor to convert the baseband signal to a stream of digital data; Digital-to-analog converter (DAC) that generates a voice waveform from the digital data; Audio amplifier; and Speaker, earphone, and/or headset. A typical data SDR replaces the DAC, Audio amplifier, and speaker back end components with a computing system accepting a data stream from the DSP stage. Typically, the demodulator and DAC functions are carried out by computer-controlled circuits whose parameters are determined by software, in an SDR.
The most significant asset of SDR is versatility. Wireless systems employ protocols that vary from one service to another. Even in the same type of service, for example, cellular telephones, the protocol often differs from country to country. A single SDR set with an all-inclusive software repertoire may be used in any mode, anywhere in the world. Changing the service type, the mode, and/or the modulation protocol involves simply selecting and executing the requisite computer program. An ultimate SDR would be a single radio transceiver capable of playing the roles of cordless telephone, cell phone, wireless fax, wireless e-mail system, pager, wireless videoconferencing unit, wireless Web browser, Global Positioning System (GPS) unit, and other functions to be later developed, operable from any location on the surface or proximate the surface of the earth, and perhaps in space as well.
The United States Department of Defense (DoD) Joint Tactical Radio System (JTRS) initiative has established an Open Standard Architecture for implementation of military communication waveforms that is specifically intended to meet a subset of these objectives. Such Joint Tactical Radio Systems are available from Rockwell Collins, Inc. of Cedar Rapids, Iowa.
There is growing interest in applying an Open Standard SDR Architecture to commercial applications such as avionics communication, navigation and surveillance (CNS). The characteristics of commercial CNS waveforms are quite different from the military JTRS communication waveforms, and, in general, are less complex to implement. A key difference between military communications and commercial avionics are the requirements associated with safety. The safety requirements associated with commercial CNS avionics typically involve gaining approval for use (generally referred to as “certification”) by the appropriate civil aviation authority, such as the Federal Aviation Administration (FAA) in the United States or the Joint Aviation Administration (JAA) in Europe. The safety requirements for the CNS functions typically address the integrity and availability, and for some functions, the continuity. Thus, it is desirable to provide an avionics commercial CNS system architecture that addresses the safety requirements while retaining compatibility with an appropriate SDR standard, preferably the Open Standard Architecture established by the DoD as part of the JTRS program.
Avionics onboard an aircraft include communication, navigation and surveillance functions. These functions provide flight crew members with the capability to communicate with ground-based facilities and control the flight of the aircraft in response to flight conditions according to flight plans. Avionics also provide passenger entertainment in airline operations.
In general, prior art avionics systems have included many dedicated pieces of equipment that each provide a function (also referred to as a waveform when radio communication is involved) to give flight crew members the ability to manually or automatically control the flight of an aircraft. Each piece of equipment (or radio) usually operates to some extent independently of the other pieces of equipment in the avionics system and performs a dedicated function throughout the entire flight. Examples of such separate pieces of equipment include a global positioning system (GPS) navigation device, a radio altimeter, a traffic alert collision avoidance system (TCAS) or a voice communication radio. Having separate dedicated pieces of equipment to perform these functions typically adds to the total equipment costs as well as the weight of the aircraft. Furthermore, having numerous separate dedicated pieces of equipment typically takes up much more volume or space, uses more power, requires more total cooling air, etc., than would be required with an integrated set of avionics equipment.
Some more recent avionics systems include one or more software defined radios (SDRs) instead of dedicated pieces of equipment. SDR essentially includes interconnected hardware and software components that are collectively capable of performing one or more avionics communication, navigation or surveillance function. As compared to the combination of multiple dedicated pieces of equipment, such SDRs are potentially less expensive to manufacture, are lighter, require less space, less power to operate, and potentially require less total cooling air.
Although avionics systems that include SDRs have the earlier-mentioned advantages over systems with dedicated pieces of equipment, in general, current avionics systems carry unutilized or under-utilized redundant equipment to meet function availability and continuity requirements during the phase of flight (dispatch, en-route, approach, etc.) where the function is used. While redundancy is necessary to meet safety critical aircraft availability requirements, excessive redundancy of limited-purpose equipment can burden the airplane infrastructure resources.
Conventionally commercial and military aircraft carry a large number of radios for specific communication, navigation and control needs. Software Defined Radios have the potential to decrease the number of radios needed on a given aircraft by changing the configuration of a radio to fit the communication need during specified times within the flight scenario. Due to certification concerns, the benefit of re-programmable modules may be limited to configurations validated during the system's qualification, verification and certification. This issue is likely to force the system to require a higher number of software definable radios than what would be necessary if the system had the freedom to change in a more dynamic way.
In particular, there is a need for SDR technology that allows a single set of hardware to perform multiple functions by software reconfiguration. Further, there is a need for reconfigurable systems that automatically and autonomously bound the dynamic behavior of the waveform allocation so that certification criteria can be met. Further still, there is a need for such a reconfigurable system that provides optimal assignments for SDR module functions.